Scilab Function
Last update : 12/1/2004

stabil - stabilization

### Calling Sequence

  `F=stabil(A,B,alfa)`
  `K=stabil(Sys,alfa,beta)`

### Parameters

- `A`: square real matrix (`nx x nx`)
- `B`: real matrix (`nx x nu`)
- `alfa, beta`: real or complex vector (in conjugate pairs) or real number.
- `F`: real matrix (`nx x nu`)
- `Sys`: linear system (`syslin` list) (`m` inputs, `p` outputs).
- `K`: linear system (`p` inputs, `m` outputs)

### Description

`F=stabil(A,B,alfa)` returns a gain matrix `F` such that `A+B*F` is stable if pair `(A,B)` is stabilizable. Assignable poles are set to `alfa(1),alfa(2),...`. If `(A,B)` is not stabilizable a warning is given and assignable poles are set to `alfa(1),alfa(2),...`. If `alfa` is a number all eigenvalues are set to this `alfa` (default value is `alfa=-1`).

`K=stabil(Sys,alfa,beta)` returns `K`, a compensator for `Sys` such that `(A,B)`-controllable eigenvalues are set to `alfa` and `(C,A)`-observable eigenvalues are set to `beta`.

All assignable closed loop poles (which are given by the eigenvalues of `Aclosed=h_cl(Sys,K)` are set to `alfa(i)`'s and `beta(j)`'s.

### Examples

    // Gain:
    Sys=ssrand(0,2,5,list('st',2,3,3));
    A=Sys('A');B=Sys('B');F=stabil(A,B);
    spec(A) //2 controllable modes 2 unstable uncontrollable modes
    //and one stable uncontrollable mode
    spec(A+B*F) //the two controllable modes are set to -1.
    // Compensator:
    Sys=ssrand(3,2,5,list('st',2,3,3)); //3 outputs, 2 inputs, 5 states
    //2 controllables modes, 3 controllable or stabilizable modes.
    K=stabil(Sys,-2,-3);  //Compensator for Sys.
    spec(Sys('A'))
    spec(h_cl(Sys,K))   //K Stabilizes what can be stabilized.

### See Also

`st_ility`, `contr`, `ppol`,